Apparatus for grinding drills



Dec. 21, 1965 A. E. AHLSTROM 3,224,146

APPARATUS FOR GRINDING DRILLS Filed May 22, 1963 2 Sheets-Sheet 1 Fig.7 d/z INVENTOR.

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AGcENT Dec. 21, 1965 A. E. AHLSTROM APPARATUS FOR GRINDING DRILLS 2 Sheets-Sheet 2 Filed May 22, 1963 United States Patent APPARATUS FOR GRINDING DRILLS Allan Eugen Ahlstriim, Nora-a Vagen 11,

Haimstad, Sweden Filed May 22, 1963, Ser. No. 282,296 Claims priority, application Sweden, May 24, 1962, 5,843/62 4 Claims. (Cl. 51-90) My invention has reference to an apparatus for grinding drills, in particular twist drills.

The main feature of the invention is that the apparatus is adapted to be clamped on the drill to be ground which is e.g. chucked in a drilling machine, and the grinding apparatus is provided with devices for driving a grinding disk by means of the rotating drill with the disk resting against the operative end of the drill, the device being adapted to be held by a hand during the grinding.

According to one embodiment of the invention the grinding apparatus comprises a telescoped central main shaft with a centering and clamping device for adjusting the drill to be ground, two grinding disks rotationally carried in the telescoped central main shaft and inclining towards each other with their peripheries touching each other at the axis of the adjusting and clamping means, one or several adjusting means adapted to engage the chip channels in the drill so as to ensure that the drill assumes the correct position relative to the telescoped central main shaft and thus also to the grinding disks so that the latter will be applied at the correct place of the operative surface of the drill, a handle at the lower portion of the apparatus to be held by the hand during the grinding and means adapted, at the rotation of the telescoped central mean shaft relative to the handle, to rotate the grinding disks abutting against the operative end of the drill clamped by the centering and clamping means so as to grind the drill edges.

Such an apparatus makes it possible to grind a drill chucked in the drilling machine quickly and easily. Thus, the drill does not have to be removed for being ground. The use of the grinding apparatus according to the invention involves a considerable gain of time. The grinding can be carried out in some few seconds.

An example of an apparatus in accordance with the invention will now be described with reference to the accompanying, partly diagrammatic drawings, in which:

FIG. 1 is a side elevation, partly cut in the longitudinal direction, on an enlarged scale of a grinding apparatus according to the invention,

FIGS. 2 and 3 show on an even more enlarged scale a cross section through the apparatus on the lines IIII and III-III, rsepectively, in FIG. 1.

1 denotes a chuck of a drilling machine for chucking a twist drill 2.

The main parts of the grinding apparatus comprise a housing or cover shaped as a handle 3 adapted, during the grinding, to be held by the hand, and a teleseoped central main shaft 4 rotating relative to the cover, said shaft in the shown embodiment comprising an upper hollow inner portion 5 and a lower hollow outer portion 6 longitudinally movable relative to said upper portion 5. The upper por tion 5 is provided at its top with a chuck 7 to hold the drill 2 in the portion 5. Below the means 7 there is arranged a guiding means for ensuring that the drill will be brought in the correct position relative to the shaft 4 for being correctly ground. Said guide means comprises according to the shown embodiment two pistons 9, 10 which are, diametrically opposite each other, radially movable in the body 8 of the means 7 and which are arranged in bores 11 in the body 8. Each bore is closed at the outer end by means of a screw 12. Between the "ice radially outer ends of the pistons 9, 1t) and the corresponding screw 12 there is clamped a helical spring 13 which presses the corresponding pistons 9 and 10, respectively, in such a way that at least one of the pistons with its inner end, shaped as a conical tenon 14 and 15, respectively, engages fixedly one of the chip channels 16 of the drill 2. Two grinding disks 18, 19 are carried in the lower portion 6 on ball bearings 17 on lateral arms 33 on the portion 6 (only one shown in PG. 1), said disks 18, 19 being inclined with an angle corresponding to the inclination of the end surfaces 20 of the drill 2 at the operative end of the same. A bevel gear wheel 22 is attached on each one of the shafts of the grinding disks 18, 19, said gear wheel 22 cooperating with a bevel gear wheel 23, the latter together with a somewhat larger bevel gear wheel 24 being journalled on an intermediary shaft 25 carried in the lower end of the portion 6. Last mentioned gear wheel 24 cooperates with a gear ring 26 with inner teeth, said ring 26 arranged concentrically to the central shaft 4 and thus also with the longitudinal axis 27 of the drill 2. A similar intermediary shaft 25 with gear wheels 23, 24 transmits via a gear wheel 22 and a shaft 21 the rotation to the grinding disk 18 (and similar to the grinding disk 19). The grinding disks 18, 19 are carried and dimensioned in such a way that their peripheries touch each other at the axis 27. The lower portion 6 is at its lower portion provided with a carrying tenon 28 by means of which the central shaft is journalled in the handle 3. The latter is preferably shaped in such a way that it can easily be held by one hand during the grinding operation. The lower portion 6 extends at its upper portion through the upper portion of the handle and is rotationally carried in said upper portion.

The upper portion 5 is provided with a longitudinal groove 29 engaged by the inner end of a screw 30 in such a way that the lower portion 6 can be axially moved a small distance corresponding to the length of the groove 29. Between the body 8 of the means 7 and the upper end of the lower portion 6 there is clamped a helical spring 31 which keeps the last mentioned portion with the handle 3 in its lower position in which the grinding disks 18 and 19 are situated at some distance below the operative end of the drill 2.

When the drill 2 in the chuck 1 needs to be reground, the grinding apparatus is from below put on the drill whereupon the automatically centering jaws of the centering and clamping means 7 are opened and automatically enclose and clamp the drill at its upper end in such a way that the axes 27 of the drill and the central shaft will coincide. When the apparatus is put on the drill simultaneously the conical tenon 14 or 15 on the pistons 9, 10 dimensioned for fitting the chip channels 16 in the drill 2 to be ground (as known, drills with varying dimensions have chip channels of varying sizes) are entered into these channels is ensured that the central shaft will assume the correct position relative to the drill 2, i.e. the grinding disks 18, 19 will with their upper border surfaces be situated close to the axis 27 in front of the end surfaces on the operative end of the drill 2. When the motor thereupon is started, the drill 2 will drive the central shaft 4 with the same rotation speed as the one of the drill. As the handle 3 is kept by the hand and thus the gear ring 26 will remain stationary, the bevel gear wheel 24 will be forced to rotate while bringing along the gear wheel 23 which transmits the driving force to the gear wheel 22, the shaft 21 and the grinding disk 18 which thereby will be driven with a considerably higher speed than the one of the drill. The same is true also for the disk 19. When thereupon the handle 3 is lifted and brings along the lower portion 6 against the action of the spring 31, the grinding disks 18, 19 are pressed against the end surfaces 20 of the drill 2 whereby the edges 32 are reground. At the end of grinding operation the grinding apparatus is removed from the drill 2 which then is ready for work. The whole grinding operation requires only some few seconds in connection with drills with a diameter of 5-10 millimetres.

The grinding apparatus can be put on the drill 2 and taken away from the same without even stopping the drill machine. Hereby the time for the grinding operation is further reduced.

So as to render possible a quick replacement of the grinding disks 18, 19 the roller bearings 17 should be enclosed in bearing halves which are easily removable from the portion 6 and after the replacement of the grinding disk again can be attached by means of screws (not shown in FIG. 1 but in FIG. 3).

As indicated with dash and dot lines in FIG. 1, it is possible to screw the hub 35 of a crank 36 on a threaded tenon 34 which can be reached below the handle 3 and which constitutes an elongation of the carrying tenon 28 for the stand portion 6. Such a device makes it possible to grind loose drills 2 which are entered from above through the centering and clamping means 7 down to the vicinity of the grinding disks 18, 19. The grinding is carried out in such a way that one with one hand holding the handle 3 and with the other hand turning the crank 36 whereby in the way described in the aforegoing the grinding disks 18, 19 are brought to rotate about ther own axes while the telescoped central shaft 4 with the drill rotates with a lower speed about the axis 27.

The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims. Of course, the apparatus can be used for grinding other drills than twist drills. The grinding operation does not have to be performed vertically but could also be performed horizontally.

What I claim is:

1. In a grinding apparatus for grinding a twist drill having at one end thereof faces having cutting edges, the drill being provided with chip channels: a hollow main shaft having lateral arms; a centering and clamping means for clamping the drill to be ground in said main shaft coaxial therewith; two inclined grinding disks rotatably carried on the arms of the shaft, the peripheries of said grinding disks close to each other near the axis of said centering and clamping means; at least one guiding means adapted to engage one of the chip channels of the drill to be ground for locating the drill correctly relative to said shaft and thus also relative to said grinding disks, the latter thereby being brought to contact the faces of the drill; a handle at the lower end of said shaft so that the apparatus can be held with one hand of the operator during the grinding operation; and means for, upon the rotation of the shaft relative to said handle, to rotate said grinding disks when the latter are in contact with the faces of the drill while the latter is clamped by said centering and clamping means so as to grind the cutting edges of said drill.

2. In a grinding apparatus as claimed in claim 1, said guiding means comprising a spring loaded piston adapted to engage one of the chip channels in the drill to be ground with its radially outer end.

3. A grinding aparatus for a twist drill provided at one end thereof with faces forming a cutting end and having chip channels comprising a normally vertical hollow handle for a housing of generally circular horizontal cross section; a main central normally vertical hollowed shaft made up of telescoped inner and outer members mounted for rotation in the handle, the inner member extending upwardly from and out of the handle; a self centering chuck for holding a drill and fast on the upper end portion of inner member for centering the drill in the hollow of the shaft, said shaft portions being movable in the direction of their axis and means for limiting said movement, a spring about the inner portion and compressed between the chuck and outer portion, said outer portion being provided with two lateral arms and adjacent openings into the hollow of the outer portion, inclined rotary grinders carried on the respective arms and projecting through said openings to engage the cutting end of the drill, and gear means for rotating the grinders about their own axes when the main central shaft is rotated relative to the handle.

4. A grinding apparatus as claimed in claim 3 in which said chuck has thereunder and thereon a body provided with opposite nearly radial bores, spring loaded cylindrical positioning members having conical inner ends to engage in the chip channels of the drill for guiding the drill in the hollow of the central shaft when the drill is inserted therein.

References Cited by the Examiner UNITED STATES PATENTS 2,017,532. 10/1935 Elter et al 51-120 2,177,644 10/1939 Finke 51-120 LESTER M. SWINGLE, Primary Examiner.

I. SPENCER OVERHOLSER, Examiner. 

1. IN A GRINDING APPARATUS FOR GRINDING A TWIST DRILL HAVING AT ONE END THEREOF FACES HAVING CUTTING EDGES, THE DRILL BEING PROVIDED WITH CHIP CHANNELS: A HOLLOW MAIN SHAFT HAVING LATERAL ARMS; A CENTERING AND CLAMPING MEANS FOR CLAMPING THE DRILL TO BE GROUND IN SAID MAIN SHAFT COAXIAL THEREWITH; TWO INCLINED GRINDING DISKS ROTATABLY CARRIED ON THE ARMS OF THE SHAFT, THE PERIPHERIES OF SAID GRINDING DISKS CLOSE TO EACH OTHER NEAR THE AXIS OF SAID CENTERING AND CLAMPING MEANS; AT LEAST ONE GUIDING MEANS ADAPTED TO ENGAGE ONE OF THE CHIP CHANNELS OF THE DRILL TO BE GROUND FOR LOCATING THE DRILL CORRECTLY RELATIVE TO SAID SHAFT AND THUS ALSO RELATIVE TO SAID GRINDING DISKS, THE LATTER THEREBY BEING BROUGHT TO CONTACT THE FACES OF THE DRILL; A HANDLE AT THE LOWER END OF SAID SHAFT SO THAT THE APPARATUS CAN BE HELD WITH ONE HAND OF THE OPERATOR DURING THE GRINDING OPERATION; AND MEANS FOR, UPON THE 